1. Field of the Invention
The present invention relates to a beam projector, and more particularly to a focus control device for a beam projector, which allows the focus of the beam projector to be easily controlled.
2. Description of the Related Art
Typically, a portable electronic device is a personally carried compact electronic communication device, such as a portable terminal, a cell phone, an MP3 player, a PMP, or combinations thereof, that can be carried personally so as to come in contact with various contents. In particular, the portable terminal is a portable electronic device that is capable of being carried personally and has at least one of voice and image communication functions, an information input/output function, and/or a data storage function. In addition, according to functional diversity, the portable terminal has composite functions, such as photographing still and/or moving pictures, reproducing music or moving picture files (multi-media), implementing games, receiving broadcasts, or the like, and is fabricated in the form of an integrated multimedia device.
In terms of software and hardware, various novel attempts are applied to such a portable device so as to implement composite functions. For example, a user interface is provided so as to allow a user to easily, and conveniently, search or select a desired function. In particular, since such a portable terminal is fabricated as a multimedia device, which is most diverse in terms of function among the various portable electronic devices, the portable terminal is equipped with electronic components, such as a camera module, a broadcast receiving module, or the like, that are required for implementing various functions beyond that of the wireless communication function of the portable terminal.
Recently, a beam projector function (an image projecting function) has been implemented in such a portable terminal. In general, a “beam projector” implies a device that forms an image on a display device, transmits light produced from a separate light source to the display device so as to project and provide the image on an external large screen.
The construction of such a beam projector is described in detail in Korean Patent No. 10-0810260 entitled, “Portable Terminal with Projector,” and Korean Patent No. 10-0735422 entitled, “Image Offset Control Device for Liquid Crystal Projector,” which were filed in the name of the applicant of the present application and published on Mar. 23, 2007 and published on May 8, 2009, respectively.
FIG. 1 shows a portable terminal with a conventional beam projector, and FIGS. 2 and 3 show a side view and an internal view, respectively, of the mounting of a beam projector in the body of the portable terminal of FIG. 1.
As shown in FIGS. 1 to 3, a beam projector 10 is mounted on one side of the body housing 1 of a portable terminal, so that a multimedia function related to a moving picture, a DMB, a game or the like, or contents stored in a memory of the portable terminal can be visualized on an external wall or an external screen 20. The beam projector 10 is provided with a window 2 for projecting an image to the one side of the body housing 1. A lens assembly 11 is provided inside of the area where the window 10 is mounted. In addition, the beam projector 10 is provided with a focus control device 3 for controlling the quality of the image projected through the lens assembly 11. The focus control device 3 has a focus control member 12 exposed to the outside. The focus control member 12 has an actuating member 13 as a control handle which can be manually manipulated by a user. The focus control member 12 is mounted in a manner to be capable of being moved rectilinearly in the direction of the optical axis of the lens assembly 11.
However, since the control handle provided to be exposed to the outside of the body housing is very small, and the inner and outer spaces for controlling the control handle are very narrow, there is a problem in that it is inconvenient for the user to slide the control handle.
In addition, since the size of a guide groove (not shown), which is provided for allowing the control handle to be moved, has a limited size, the control handle must be slid within a restricted space. In addition, the control handle is caused to stop at the opposite ends of the guide groove while it is being slid. Consequently, there is a problem in that the control handle is very poor in terms of mobility.